Question: Why is it that only planet earth has an ozone layer ?

Daniel Parsons answered on 10 Nov 2014:

Good question, but quite a complicated one!
Ozone is a molecule that has three oxygen atoms stuck together. It is made in the atmosphere when ultra-violet (UV) light from the sun reacts with oxygen in the atmosphere, that then binds three oxygen atoms together. However, UV light also destroys ozone, so you need just the right mix of oxygen and UV light and form Ozone. In these reactions Ozone is made, broke-up and remade all the time. Other planets in our solar system don’t have this right mixture.
Our Ozone layer is important as it absorbs the harmful UV light in the upper atmosphere. If it was not there then most living things (like us) on the surface of Earth would be damaged by UV light and burn very easily like when you burn when in the Sun too long in the summer – only without the Ozone layer it would take a fraction of the time!